Unable to Create EcoreEditorID Editor

java.lang.ClassCastException: org.apache.xerces.jaxp.SAXParserFactoryImpl cannot be cast to javax.xml.parsers.SAXParserFactory
at javax.xml.parsers.SAXParserFactory.newInstance(Unknown Source)
at org.eclipse.emf.ecore.plugin.EcorePlugin.computePlatformPluginToPlatformResourceMap(EcorePlugin.java:302)
at org.eclipse.emf.ecore.plugin.EcorePlugin.computePlatformURIMap(EcorePlugin.java:424)
...

It looks like this occurs when two plugins register two different SaxParserFactorys.

In my case, it seems it was that I had both the Ecore and ATL plugins installed at the same time; removing the ATL plugin resolved this error.